1. Field of the Invention
The present invention relates to an improved catalyst for polymerizing olefins, a method for producing such a catalyst and to a method of polymerizing olefins, preferably alpha-olefins, with such a catalyst. A particular aspect of the present invention relates to a method for preparing a high activity olefin catalyst composition, supported on a novel support, which is not sensitive to usual olefin polymerization catalyst poisons.
2. Description of the Prior Art
Linear low density polyethylene polymers possess properties which distinguish them from other polyethylene polymers, such as ethylene homopolymers. Certain of these properties are described by Anderson et al, U.S. Pat. No. 4,076,698.
Karol et al, U.S. Pat. No. 4,302,566, describe a process for producing certain linear low density polyethylene polymers in a gas phase, fluid bed reactor.
Graff, U.S. Pat. No. 4,173,547, Stevens et al, U.S. Pat. No. 3,787,384, Strobel et al, U.S. Pat. No. 4,148,754, and Ziegler, deceased, et al, U.S. Pat. No. 4,063,009, each describe various polymerization processes suitable for producing forms of polyethylene other than linear low density polyethylene, per se.
Graff, U.S. Pat. No. 4,173,547, describes a supported catalyst obtained by treating a support, e.g., silica, with both an organoaluminum compound and an organomagnesium compound followed by contacting the treated support with a tetravalent titanium compound.
Stevens et al, U.S. Pat. No. 3,787,384, and Stroebel et al, U.S. Pat. No. 4,148,754, describe a catalyst prepared by first reacting a support (e.g., silica containing reactive hydroxyl groups) with an organomagnesium compound (e.g., a Grignard reagent) and then combining this reacted support with a tetravalent titanium compound. According to the teachings of both of these patents, no unreacted organomagnesium compound is present when the reacted support is contacted with the tetravalent titanium compound.
Ziegler, deceased, et al, U.S. Pat. No. 4,063,009, describe a catalyst which is the reaction product of an organomagnesium compound (e.g., an alkylmagnesium halide) with a tetravalent titanium compound. The reaction of the organomagnesium compound with the tetravalent titanium compound takes place in the absence of a support material.
A vanadium-containing catalyst, used in conjunction with triisobutylaluminum as a co-catalyst, is disclosed by W. L. Carrick et al in Journal of American Chemical Society, Volume 82, page 1502 (1960) and Volume 83, page 2654 (1961).
Nowlin et al, U.S. Pat. No. 4,481,301, disclose a supported alpha-olefin polymerization catalyst composition prepared by reacting a support containing OH groups with a stoichiometric excess of an organomagnesium composition, with respect to the OH groups content, and then reacting the product with a tetravalent titanium compound. The thus-obtained catalyst is then activated with a suitable activator, e.g., disclosed by Stevens et al, U.S. Pat. No. 3,787,384 or by Stroebel et al, U.S. Pat. No. 4,148,754. The preferred activator of Nowlin et al is triethyl-aluminum. Nowlin et al, U.S. Pat. No. 4,605,638 and Nowlin, U.S. Pat. No. 4,593,009, disclose variations of the catalyst composition of the Nowlin et al U.S. Pat. No. 4,481,301.
Karol et al, European Patent Application 84103441.6, filed Mar. 28, 1984, Publication Number 0 120 503, published on Oct. 3, 1984, disclose a catalyst composition prepared in a process comprising forming a precursor composition from a magnesium compound, a titanium compound and an electron donor compound and then diluting the precursor composition with an inert carrier, such as silica.
The entire contents of all of the aforementioned publications, patents and patent applications are incorporated herein by reference.
Silica, alumina or silica-alumina cogels have been commonly used in the past as supports for Ziegler alpha-olefin polymerization catalysts. Such refractory support materials are available in a variety of particle sizes and porosities and their usefulness as catalyst supports is well documented in the art. However, such supports have several deficiencies. For example, they must be calcined at high temperatures to remove water which is a common catalyst poison. In addition, they have a limited maximum pore size which restricts catalyst performance. It has been found that increased pore size improves the properties of Ziegler alpha-olefin polymerization catalysts, e.g., see copending application, Ser. No. 805,634, filed on Dec. 6, 1985 and now abandoned. Unfortunately, large pore size refractory materials may be friable and the use thereof as catalyst supports may lead to the formation of unwanted fine particles through attrition. Additionally, refractory oxide support materials readily adsorb commonly-occurring catalyst poisons, such as oxygen and water.
Refractory oxide supports have also been commonly used as supports for catalysts used to polymerize olefins other than alpha-olefins, such as styrene, and derivatives thereof. The use of refractory oxide supports for such vinyl olefins catalysts also presents some practical and operational problems.
Accordingly, a need still exists in the art for providing an improved supported catalyst composition which is relatively insensitive to catalyst poisons and non-friable and the support material of which need not necessarily be dehydrated, thereby reducing the overall cost of preparation of the catalyst composition.
These and other objects of the invention will become apparent to those skilled in the art from the following description thereof and the appended claims.